CHM 211 Exam 2: Fall 2018 PDF

Exam 2 Name: CHM 211 Constants: R= 0.0821 L-atm/mol-K Part I. Multiple Choice. Circle the single, best answer. (6 pts each) 1\. According to valence bond theory, which orbitals on bromine atoms overlap in the formation of the bond in Br~2~? a\) 3s b) 3p c) 4s d) 4p e) 3d 2\. Which type of mole...

Exam 2 Name: CHM 211 Constants: R= 0.0821 L-atm/mol-K Part I. Multiple Choice. Circle the single, best answer. (6 pts each) 1\. According to valence bond theory, which orbitals on bromine atoms overlap in the formation of the bond in Br~2~? a\) 3s b) 3p c) 4s d) 4p e) 3d 2\. Which type of molecular orbital is used to describe a buildup of electron density along the axis connecting two atomic nuclei to form a bond? a. σ b) π c) σ\* d) π\* e) p~y~ 3\. The O~2~ diatomic molecule has \_\_\_\_\_\_ unpaired electrons and a bond order of \_\_\_\_\_\_. a\) 0, 1 b\) 1, 1 c\) 2, 2 d\) 0, 2 e\) 3, 0 4\. A mixture of CO~2~ and an unknown gas was allowed to effuse from a container. The unknown gas effused 1.25 times faster than the CO~2~. Which one could be the unknown gas? a. Cl~2~ b) SO~2~ c) HCl d) H~2~ e) CO 5\. The reaction of 5.00 L of N~2~ gas with excess H~2~ gas to form NH~3~ gas via the equation: N~2~(g) + 3 H~2~(g) → 2 NH~3~(g) will produce \_\_\_\_\_\_ L of NH~3~ if the pressure is 1.0 atm and the temperature is 273 K. a. 2.50 L b) 5.00 L c) 10.0 L d) 15.0 L e) 20.0 L 6\. An ideal gas differs from a real gas in that the molecules of an ideal gas: a\) have no attraction for one another b\) have large molecular volumes c\) have a molecular weight of zero d\) have no kinetic energy Part II: Discussion Questions (**you must show all of your work to receive credit**). Be sure to include units where applicable. 1. Consider a molecule that contains a central atom with 4 total electron pairs around it. Circle all of the following that would be true about this molecule: (6 pts) a. The central atom is sp^2^ hybridized. b. The molecule could never contain a double bond. c. The molecule would always be polar d. The electron-pair geometry is always tetrahedral 2. What molecular geometries are possible for a molecule with the formula AB~4~? (4 pts) b\) What molecular geometries are possible if there are 3 total electron pairs around the central atom? (4 pts) 3\. Indicate whether each statement below about gases is true or false: (10 pts) a. Gases form homogeneous mixtures with each other. \_\_\_\_\_\_\_\_\_\_\_\_\_ b. The total pressure of a mixture of gases equals the sum of the partial pressures exerted by each gas in the mixture. \_\_\_\_\_\_\_\_\_\_\_\_\_ c. Molecules of different gases at the same temperature always have the same average kinetic energy. \_\_\_\_\_\_\_ d. The larger the gas, the faster it would diffuse. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ e. A real gas deviates from an ideal gas at high temperatures and high pressures. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 4\. A 9.5 L container holds a mixture of two gases at 75 °C. The partial pressures of gases A and B respectively are 0.39 atm and 0.45 atm. If 8.0 g of CO~2~(g) is added with no change in temperature or volume, what will the total pressure become? 5\. The thermal decomposition of potassium chlorate can be used to produce oxygen in the lab: (8 pts) 2 KClO~3~(s) → 2 KCl(s) + 3 O~2~(g) How many grams of KClO~3~ would need to decompose to produce 5.0 L of oxygen at STP? (T=0°C and P=1.0 atm) 6\. A) Draw the **Lewis structure** B) Give the **molecular geometry** and C) Tell whether the molecule is **polar or nonpolar** (12 pts) a\) SO~2~ b) XeF~5~^+^ 7\. The molecule shown below is the pain reliever ibuprofen. Answer the following questions for the compound shown below: (14 pts) a. How many total π bonds are in the molecule? \_\_\_\_\_\_\_\_\_\_\_\_\_\_ b. What are the approximate values of the labeled bond angles? d\) What are the **molecular geometries** for the labeled central atoms? Central Atom C \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Central Atom D \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_